<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        let p = new Promise((res,rej)=>{
            res('ok')
            // rej('error')
            // throw 'error'
        })

        p.then(val=>'123').then(val=>console.log(val)).then(val=>console.log(val))

        // let p2 = p.then(val=>{
        //     return '123';
        // })

        // let p3=p2.then(val=>{
        //     console.log(val);
        //     // return val;
        // });

        // p3.then(val=>{
        //     console.log(val);
        // })



    </script>
</body>
</html>